High-activity catalysts which are produced from an organoaluminum compound, an electron donor, and a halogenated titanium compound on a solid carrier containing various magnesium compounds, are known for polymerizing .alpha.-olefins. The most commonly used magnesium compound is anhydrous magnesium chloride, either alone or together with other magnesium compounds, or organic magnesium compound manufactured by halogenating organic magnesium compounds with compounds containing chlorine. For convenience of reference, the halogenated titanium-containing compound is referred to herein as "procatalyst" the organo-aluminum compound, as "cocatalyst" and an electron donor compound, which is typically used separately or partially or totally complexed with the organoaluminum compound, as "selectivity control agent" (SCA). It is also known to incorporate electron donor compounds into the procatalyst. The electron donor which is incorporated with the titanium-containing compounds serves a different purpose than the electron donor referred to as the selectivity control agent. The compounds which are used as the electron donor may be the same or different compounds which are used as the selectivity control agent. The above-described stereoregular high activity catalysts are broadly conventional and are described in numerous patents and other references including Nestlerode et al, U.S. Pat. No. 4,728,705, which is incorporated herein by reference.
Kioka et al, U.S. Pat. No. 4,330,649, describe a solid catalyst component (procatalyst) obtained by heating a soluble magnesium compound such as magnesium chloride with a higher alcohol in the presence of an ester to produce a solution. This solution is added to titanium tetrachloride and an electron donor to form the procatalyst. Band, U.S. Pat. No. 4,472,521, reacts a magnesium alkoxide with excess titanium alkoxide, wherein each alkoxide has 4 or more carbons in the presence of aromatic hydrocarbon. Titanium tetrachloride and an electron donor are added to the resulting solution to produce a solid procatalyst which is posttreated with transition metal halide.
A number of the more attractive olefin polymerization procatalysts are produced from magnesium alkoxides wherein the alkoxide moieties have one or two carbon atoms. Magnesium ethoxide appears to be a particularly attractive procatalyst precursor. The use of magnesium ethoxide poses a somewhat unique problem in that, unlike most other magnesium alkoxides, magnesium ethoxide is only slightly soluble in the corresponding alkanol, i.e., ethanol. Various measures have been proposed for the solubilization of magnesium alkoxide including the formation of complex magnesium ethoxides as disclosed by Job, U.S. Pat. No. 4,710,482.
Several procedures have been disclosed which involve the solubilization of magnesium ethoxide by reaction with carbon dioxide in ethanol. Arzoumanidis, U.S. Pat. No. 4,540,679, produces an olefin polymerization catalyst component by contacting a suspension of magnesium ethoxide in ethanol with carbon dioxide. To the resulting solution is added an organoaluminum compound in hydrocarbon solution to produce granular particles which are employed as a support for the titanium species which result from contacting the granular particle with titanium tetrachloride. Nestlerode et al, U.S. Pat. No. 4,728,705, react magnesium ethoxide in ethanol with carbon dioxide to form a solution. This solution is spray dried to produce particles or alternatively is used to impregnate carrier particles. The particles resulting from either modification are useful in the production of an olefin polymerization procatalyst of particularly desirable morphology.
The reaction of magnesium ethoxide with carbon dioxide in ethanol produces a soluble complex containing moieties of magnesium, ethoxide and carbon monoxide which is often referred to as carbonated magnesium ethoxide ("CMEO"). The precise structure of the complex is somewhat uncertain but a low pressure stable form is believed to be illustrated by the formula ##STR2## where x is a number from 1 to 2, and the complex is soluble in ethanol. Although the above references teach methods of converting this carbon dioxide-containing complex into olefin polymerization procatalysts and thence to olefin polymerization catalysts, it would be of advantage to provide improved olefin polymerization procatalysts and resulting catalysts from the carbonated magnesium ethoxide complex having improved activity, and increased selectivity for isotactic polypropylene.